Honestly? It really depends.
For example, Poland has always been a Sony-strong country. Nintendo properly entered the market with the N64, which at the time seemed less interesting than the PlayStation - it was more expensive and it had a limited amount of more expensive games. While the Game Boy Colour (I don't think the big one or the Pocket were available in stores - they were mostly shipped from abroad by the wealthier people or by those who had family abroad, similarily to other systems before the 32-bit era) was quite strong sales-wise due to a complete lack of opposition (the popularity of Famiclones and the Pokemon Anime also played a huge role), this is no longer the case with the DS and subsequent systems. This is practically Sony Land.
According to Maciej Kmiołek, Marketing Director of SCE Poland, the PSVita sold more units in the first two days since its launch than the 3DS throughout 2011, and judging from what I can observe myself, I am willing to believe that.
The 3DS literally *isn't* marketed at all as of now - I've only seen one commercial of it concerning Zelda OoT 3D, but that was ages ago. Not a single billboard, nothing. The Vita on the other hand is all around the place, mostly on huge billboards, not to mention the Vita launches that were held here - can't say I remember a 3DS launch at all.